The optical properties of a series of high refractive index polyphosphazenes were investigated. The wavelength-dependent change in refractive index (optical dispersion) associated with two selected polymers was examined using variable-angle spectroscopic ellipsometry. Values of the Abbe number for these polymers were calculated. These systems have a nu(D) = 20-25, which compares closely with other organic polymers with similar refractive indices. Calculation of the molar refractivity (R-m) associated with the [N=P] repeat unit structure yielded a value of R-m[N=P] = 14.36 cm(3)/mol. This value is compared with other polymer repeat unit structures. The comparison indicates that the [N=P] repeat unit has a linear polarizability close to that found in conjugated [C=C] bonds.